SRK & Solo limited to North Anerica

[paravil]

One of the main reasons for deciding to reclaim my down payments on both of these vehicles was that the only reason why they are three wheelers (and not four) is the legal requirement in North America limiting registration in the quad category to three wheels. Thus the Reanault Twizy would need to go through automobile testing procedures in North America, and inherently unstable three wheel quads are manufactured, whereas four wheels would be undisputedly safer (please read the very interesting page on James´ Australian Tilting Vehicles site: http://www.tiltingvehicle.net/AXP.html). It will be interesting to see how a comparatively fast Solo will comply with safety issues when cornering during its US compliancy tests.

Neither the Solo nor the SRK would be likely to sell in any other market where four wheels are not excluded from the quad category.

[DanCooper]

I calculated the SSF (Static Stability Factor) for the SRK, based on the specifications and my estimate of center of gravity position from photos. It comes to 1.13. Not as good as most cars but within the range of SUVs and pickups. So I would not corner real aggressively. Stability increases while braking and turning, but it decreases while accelerating and turning, so don't take that to an extreme. A big safety factor is the roll cage and the harness. Most rollover fatalities are from not wearing seat belts.

A three wheeler does have an aerodynamic advantage over a 4-wheeler. A 4-wheeler must either be wider, or it must have 4 outboard wheels instead of 2. The Solo would have a bit less drag than a 4-wheeler, because of not having rear fenders and wheel wells.

I am very skeptical of claims that a tilting vehicle will be more stable. You might claim a higher SSF because of the tilt, but that only applies to a stable turning situation. Consider a pothole. You run the right side wheels into the pothole. The tilt system compensates, lowering the right wheels and raising the left wheels to keep the vehicle upright. Then you come out of the pothole. There is no way an active control system can react quickly enough. The wheels are still tilted, and the edge of the pothole throws you over.

The regulatory issue is important. I believe that US safety and environmental regulations have been dishonestly skewed to exclude fuel-efficient cars. When I lived in France I had a Citroen BX, a mid-size car that had better fuel efficiency than anything you can get in the USA, including a Prius. In Italy you see a lot of small 3-wheel trucks. They exist mainly because they are taxed lower than 4-wheel trucks.

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I would like to see someone take an SRK (not mine), stop on dry pavement, turn the steering hard to one side, and start up at full throttle. If it doesn't roll over for that, it probably won't for other situations. If it does roll over, I still wouldn't worry about driving it, I would just know not to do that.

[SparkE]

I would like to see someone take an SRK (not mine), ...

That part made me laugh.

"Somebody try this (but you can't use MY vehicle!!)"

[paravil]

Dan .... I wouldn´t advise taking any small three (or four) wheeled vehicle at speed through a pothole. AND .... BTW .... a narrow, tilting four wheeled vehicle is the nearest thing to a `safe´ motorbike (and has many advantages over both a car AND a motorbike). A non-tilting three wheeler is alway going to be a bit of a death trap .... especially if it´s fast and has a single, rear wheel drive.

[DanCooper]

Anything is a death trap if you drive it stupidly. I don't worry about taking a 2-wheeler through a pothole - I do it often rather than swerve in traffic. A 3-wheeler with a passive tilt system (Piaggio MP3) would act like a 2-wheeler except for parking, and you can put your feet down if it starts to tip. But a narrow vehicle with active tilt and you can't put your feet down, I think is trouble. I design control systems and I have never seen a control and actuator system that could react anywhere near fast enough to follow road irregularities at reasonable driving speeds.

As far as I know, the only reason a 3-wheeler would be hazardous is that it can tip more easily than a 4-wheeler with the same track width. The effective track is the track width multiplied by the fraction of the weight on the two wheels (front or back). If the track is wide enough and the center of gravity is low enough, it could be as stable as a 4-wheeler.

I have seen an SUV roll over, going straight on a gravel road. The cause was a combination of a lower SSF than a car, washboard, and poor driving technique.

[paravil]

,,,, except that a three-wheeler has THREE tracks (instead of the two for a four wheeler .... or ONE for a two-wheeled motorbike). This makes it more than likely to `find´ the pothole (or to fail to avoid it).

Most concept narrow, tilting urban vehicles cut off the tilting function below a certain speed (ususally 5 kmh).

[Kepesk]

My two cents:

Of course a 3 wheeled vehicle will be less stable than a 4 wheeled vehicle of similar dimensions.  I don't know much about the Solo, but as far as the SRK is concerned, a whole lot of the basic design efforts of the current generation was getting the centers of gravity of various components just right, so that the thing would be as stable as possible.

While at a certain point there is no getting around the fact that it's a lightweight vehicle with less wheels, they seem to have done a superb job getting it to hug the road as tight as possible.  The thing drives like it's on rails.

[paravil]

Agree .. of the two, the SRK (front wheel drive) could be expected to be more stable, and therefore safer. Neither have yet been idependently tested. But videos of Kroll driving his Solo around town show that he´s very careful when turning corners.

[Rickb]

What's not to understand about the term "cat-like balance" used to describe the SRK?

The SRK is plenty stabile for me the way I drive a vehicle. Paravil, wait for the track testing results before making assumptions regarding the stability of the SRK and Solo. My assumption is you will be pleasantly surprised by the stability of both three wheeler EV's.

[paravil]

Rick ....you are the living proof of the victory of hope over experience! But you´re right ... I´m a born again pessimist.